My right lat is NOTICEABLY bigger than my left one. (Besides switching hands) I decided to do unilateral movements for my lats.

I start my Back workouts with one hand pull-ups in the assisted pullup machine. Besides an interesting observation that a two handed pullup could take more weight than the sum of two one-handed pull-ups, I noticed both sides were about as strong as each other. There were no strength imbalances between the two lats.

Why then , is my left lat noticeably smaller than my right one? I'm dumbstruck with this one.

Did you use to play any sports that would use one side more than the other when you were younger? I had this problem too since I played competitive tennis when I was young. Even before I started training my left lat was more developed.

However, for me, it pretty much just balanced out over time.

I've never thought to do one-handed pullups in the counterbalance machine. Do you actually feel your lats doing that?

I have this exact same problem. I also have a pinching sensation under my left shoulder blade that several physical therapy and massage student friends of mine think might be pinching a nerve that goes to my lat. I'm hopefully going to see an ART guy about it next week.

Muscle insertions? Are they the same on both sides? Just a guess but how do you even know your fiber distribution is the same in each lat (your a mutant ). Also what about your biceps? Is one stronger than the other? Not to mention all the other muscles used in the chinup. Also you beat off with your right hand no? And aren't you the one who's always pissed off? I bet you smash your hand down on tables alot in fits of rage. See more volume for you right lat!

My left lat was smaller than the right also but not weaker. I had a few sessions of ART for a shoulder injury on my left side (which is still messed up so I'm still going to the ART guy) and found out one of the problems was my left lat being to tight and pulling on my shoulder which in turn was pulling on my bicept also causing bicept tendonitis. I'm not sure if it's possible but it looks like they are the same size now after only 2 sessions.